water lubricated shaft seals

[Erwin Swart]

I am considering to change to a water lubricated shaftseal on my Moody 31 but after reading some articles I am not sure and have some questions

1) Do I only need to change the shaft bearing plus seal or also the shaft itself? I can imagine that at the position of the current bearing the shaft is worn and will give problems.

2) do I need to make a new hull through which will be connected to the seal for feeding water?

3) when placed what kind of service does it need

4) I am located in The Netherlands and stay afloat (now on ice). Does it need some winterising service?

5) which seal do you have good experience

I am quit happy with the current system and there is not a real need to replace. I am only sick of the wet bilges and alway keeping an eye on it.

Does somebody else already did this job on a M31?

Thanks for your respons

 

[nimbusgb]

1) You will need a nice, clean and true section of the shaft for the seal lips to run on.

2) - My water lubricated seal is fed from a take-off point in the riser to the anti syphon loop that is in line between the raw water pump outlet and the heat exchanger inlet. At least one boat i know has disconnected the water feed to the seal and relies purely on the outside water to provide the lubrication without any apparent ill effects.

3) bit of grease once a season. Burp it when going in the water apart from that very little. ( recommended to change every 5 years but very few are changed with anything like that frequency )

4) Hmm. If the seawater freezes in it it may split or leak. but if the seawater freezes to the depth of your shaft seal I suspect you may have more trouble than a leaking shaft seal!

5) Volvo

Wouldn't it be better to refurbish your current shaft and seal?

 

[MoodySabre]

I would have put a Volvo seal on my Moody31 but the size of lip on the sterntube was greater than the size quoted for a Volvo seal - although some say this is not a problem.

In the end I fitted a Tides Marine Seal

I took the water feed from the water pump - there is only a short piece of hose at that point so I made a loop and a T off that. The water flow is adjusted by a jubilee clip on the feed hose.

No servicing required. After 3 years in the sandy waters of East coast I get a tiny dribble but I don't do anything on a regular basis. Good piece of kit but not cheap.

You have to ensure that the seal is on a perfect area of the shaft.

 

[PeterGibbs]

1) You will need a nice, clean and true section of the shaft for the seal lips to run on.

2) - My water lubricated seal is fed from a take-off point in the riser to the anti syphon loop that is in line between the raw water pump outlet and the heat exchanger inlet. At least one boat i know has disconnected the water feed to the seal and relies purely on the outside water to provide the lubrication without any apparent ill effects.

3) bit of grease once a season. Burp it when going in the water apart from that very little. ( recommended to change every 5 years but very few are changed with anything like that frequency )

4) Hmm. If the seawater freezes in it it may split or leak. but if the seawater freezes to the depth of your shaft seal I suspect you may have more trouble than a leaking shaft seal!

5) Volvo

Wouldn't it be better to refurbish your current shaft and seal?

Just to endorse the Volvo seal, which I used for 9 years successfully. No seal is a fit and forget job but this one is pretty forgiving. A little grease inserted from the inside end once a season, a burp to ensure water contact thoughout the seal -the main lubrication job is performed by seawater running up the shaft. Hardly ever a drop of water passed this setup.

New shaft? The Volvo seal does not demand a pristine metal surface to work - but I would estimate that any incisions (more than just light wear) in the shaft by way of the seal lip area will result in degredation of the seal over time. It may be possible to smooth the contact area on the shaft before fitting the seal and avoid the cost of a new one - worth considering.

PWG

 

[Conachair]

I am considering to change to a water lubricated shaftseal on my Moody 31 but after reading some articles I am not sure and have some questions

1) Do I only need to change the shaft bearing plus seal or also the shaft itself? I can imagine that at the position of the current bearing the shaft is worn and will give problems.

2) do I need to make a new hull through which will be connected to the seal for feeding water?

3) when placed what kind of service does it need

4) I am located in The Netherlands and stay afloat (now on ice). Does it need some winterising service?

5) which seal do you have good experience

I am quit happy with the current system and there is not a real need to replace. I am only sick of the wet bilges and alway keeping an eye on it.

Does somebody else already did this job on a M31?

Thanks for your respons

If your current system is a stuffing box then PTFE packing might be worth a go.
http://www.asap-supplies.com/marine/packing/ptfe-packing-per-metre
Mine needs repacking now after 5 years of drip free service.

 

[doug748]

This would be worth looking at:

http://www.ybw.com/forums/showthread.php?t=253274&highlight=stern+gear

 

[Ruffles]

1) Do I only need to change the shaft bearing plus seal or also the shaft itself? I can imagine that at the position of the current bearing the shaft is worn and will give problems.

Did this some years ago.
If you're replacing the traditional stern gland fitted by Moody with a Volvo Penta seal then the bearing point will NOT coincide with the wear point on the shaft.
The only downside is that the stern tube is slightly larger than that specified by VP. Turned out not to be a problem for me. The clamp ring doesn't fully close but no big deal. Some people have used the 25mm shaft version but a 1" version is available.
The VP seal doesn't require water injection. But this means you need to burp the air out after launching. And occasionally when the boat's been lying idle for a while. Farting shrimps presumably.

You'll need to pull the shaft to fit it. If you've not done this before invest in a proper set of punches to remove the pins.

Just found my notes on Google Docs. Part number I used was 3819724.

 

[davidej]

I had a M31 with a leaky stuffing box.

Because of the sizes of the stern tube/ prop shaft a volvo seal would not fit- my boat at least.

I fitted a PSS system and it was excellent. it does not seal against the shaft so you dont have to worry about wear grooves

 

[davidej]

Another point

After fitting the PSS I stll had wet bilges. After hour of tracing the source, I fould that water had got into the wooden block thru which the P-bracket is mounted. This had swollen and made a hair-line split in the GRP encapsulation. This was the cause of a slight weep of water.

Worth checking!

 

[PetiteFleur]

I had a M31 with a leaky stuffing box.

Because of the sizes of the stern tube/ prop shaft a volvo seal would not fit- my boat at least.

I fitted a PSS system and it was excellent. it does not seal against the shaft so you dont have to worry about wear grooves

I fitted a Volvo seal on my Moody 33 when I re-engined - as said the original fitting on the hull is not suitable - but mine was damaged and worn so I had a new one made by a local firm in Norfolk to suit the Volvo seal. From memory made from Phosphor Bronze and cost about £50. Well pleased and the Volvo seal doesn't leak(even though I've forgotton to 'burp' it once or twice). I used the 25mm version on a 1" shaft.

 

[Tranona]

I used the 25mm version on a 1" shaft.

Why would you do that when the correct size is freely available?

To the OP try and use a Volvo seal if you can (making sure it is exactly the right size). It is simple and cheap - you should not need to remove the shaft, only the coupling to move the shaft back and it does not need a water feed. Next best thing is a Tides Marine as it also uses a lip seal , but it is more complicated, usually needs a water feed and much more expensive.

 

[multihullsailor6]

On my cat both deep-sea driveshaft seals started to leak around the same time! The boatyard in La Coruna fitted two Tides Marine seals without making a connection for a water feed, assuring me it is not needed as they had fitted many of these like that for years without problems in use - so far so good! The shafts did not to be removed when the work was undertaken but we did have to beach my boat on the local slipway.